MnOx location on MnOx-ZSM-5 to influence the catalytic activity for selective catalytic reduction of NOx by NH3

Abstract

MnOx-ZSM-5 catalysts with different MnOx location were synthesized and their catalytic performances are investigated for selective catalytic reduction of NOx with NH3 (NH3-SCR). MZ-150 that MnOx clusters are dispersed on the outside of ZSM-5 exhibits higher catalytic activity at low temperature than MZ-25 of MnOx nanoparticles encapsulated in the channels of the support. The characteristics results show that the excellent redox ability and the dominant Mn3+ species over MZ-150 improve the oxidation of NO to NO2 and the formation of unstable NOx intermediates, enhancing the low-temperature SCR activity. For MZ-25, the confinement effect of ZSM-5 leads to a large NOx adsorption capacity, but the generated NOx species are stable, which could be the important reason for the poor activity at low temperature. This work reveals the relationship between the location of MnOx nanoparticles and the SCR properties, which can provide a new idea for designing the low-temperature zeolite catalysts.